This disclosure relates to improvements in measurement and calibration of apparatus used for testing the track strength of railroad track, tie and fastener conditions using a loaded gauge axle assembly which imparts a calibrated downward force and a calibrated outward force on the rails, and measures the load applied to the rails to determine the strength of the rails, ties and fasteners.
By way of background but not limitation, various types of measurement and calibration devices are utilized by the industry for testing strength of railroad tracks, ties and fasteners including a “Gauge Restraint Measurement System (GRMS)” from the U.S. Department of Transportation also described in an article entitled “AAR's Track Loading Vehicle” and U.S. Pat. No. 5,756,903 issued May 26, 1998. The teachings of said U.S. Pat. No. 5,756,903 are incorporated by reference as if fully set forth herein.
The track strength testing vehicle of U.S. Pat. No. 5,756,903 measures changes in hydraulic fluid pressure to determine both changes in load due to track strength changes and to control the load applied.
This system introduces potential error in the measurements because of factors such as time lag between changes at the wheel and measurement of pressure, errors-introduced by pressure changes made to preserve load at the wheel, and the number of components, instruments and calculations involved. This system does not account for frictional forces within the split-axle assembly and cannot be used as a true rail/wheel force through direct transducer measurement.
While the track strength testing taught in U.S. Pat. No. 5,756,903 is believed to be reliable and cost effective, its measurement system is believed to be somewhat over-inclusive, in that the statistical variations result in indications of track failure, when in fact the track is within specifications. Improved accuracy, therefore, can be expected to have economic and time saving benefits in minimizing unnecessary repairs, and operational benefits in the ability to reliably and rapidly locate those areas in need of repair.
The testing apparatus of U.S. Pat. No. 5,756,903 is a significant improvement over the very large sized competitive track testing machines in that the load gauge axle assembly can be comparatively easily removed and replaced, both for maintenance, and also for calibration. Under the arrangement of U.S. Pat. No. 5,756,903 complete calibration is accomplished by removal of the axle assembly and testing in a laboratory or shop. Field calibration can only be accomplished on certain components and systems. Rail car mounted testing apparatus, or track maintenance apparatus the size and mass of rail cars are even more difficult to calibrate, as the size of the vehicle and its components essentially requires removal from service and return to a shop.
In view of the above, it should be appreciated that there is a need for a device that accurately measures track strength and permits expedient calibration of the measurement device. The present disclosure satisfies these and other needs and provides further related advantages.